Muffler assembly

ABSTRACT

A muffler assembly is provided including a diffuser adapted to expand exhaust gas entering the muffler assembly, an insert with at least one opening through which exhaust gas passes to exit the muffler assembly, and a baffle-less sound dampening portion to muffle engine sound. Preferably, the muffler assembly is of a double walled configuration with insulation provided between an inner wall and an outer wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to muffler assemblies, and more particularly to motorcycle muffler assemblies.

2. Description of the Related Art

Muffler assemblies are known. Exemplary muffler assemblies are disclosed, for example, in U.S. Pat. Nos. 4,574,914; 5,183,130; 5,979,583; and 6,267,193, which are all incorporated by reference herein in their entirety. Other muffler assemblies also exist.

When designing a muffler, it is advantageous to achieve a relatively high gas flow rate, as increased gas flow often leads to an increase in engine performance. However, increasing the gas flow rate also tends to decrease a given muffler's sound dampening performance. Hence, known muffler assemblies tend to be either quiet and low performing, or loud and high performing. Thus, a need exists for an improved muffler assembly that is relatively quiet, with an improved gas flow rate.

The aforementioned problem of designing a quiet, high performance muffler is particularly difficult in applications involving relatively tight size and orientation constraints. By way of example, in motorcycle applications it may be desirable to hide as much of the muffler assembly as possible for cosmetic reasons. Similarly, it may be desirable to orient exposed regions in such a way that more aesthetically appealing portions (e.g., chromed surfaces) are the regions most readily visible by a bystander, again for cosmetic reasons. Similar considerations may apply in other contexts, such as all terrain vehicles (ATVs), snowmobiles, boats (particularly with inboard engines), and jet skis. In these applications, it is even more difficult to achieve a relatively quiet, high performance muffler without adversely impacting the vehicle's aesthetics.

Other problems with the prior art not described above can also be overcome using the teachings of the present invention, as would be readily apparent to one of ordinary skill in the art after reading this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a top view of a muffler assembly according to an embodiment of the present invention.

FIG. 2 depicts a cross sectional view along plane A-A of the muffler assembly of FIG. 1.

FIG. 3 depicts a cross sectional view along plane B-B of the muffler assembly of FIG. 1.

FIG. 4 depicts a cross sectional view along plane C-C of the muffler assembly of FIG. 1.

FIG. 5 depicts a side view of the muffler assembly of FIG. 1.

FIG. 6 depicts a cross sectional view along a length of the muffler assembly of FIG. 5.

FIG. 7 depicts another cross section view along a length of the muffler assembly of FIG. 5, including an insulating material according to an embodiment of the present invention.

FIGS. 8-14 depicts a muffler assembly according to another embodiment of the present invention, with optional mounting brackets.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

A muffler assembly for a motorcycle according to an embodiment of the present invention is shown in FIGS. 1-7. The motorcycle may include, for example, a V-twin engine, or other suitable motorcycle engine. Other applications, such as ATVs, snowmobiles, boats, and jet skis are also contemplated.

As shown in FIGS. 1-7, the muffler assembly preferably includes at least three sections: a diffuser section 110, a muffling section 120, and a third section with a removable end cap 130. Each of diffuser section 110, muffling section 120, and removable end cap 130 will be described individually below for purposes of illustration only. It should be appreciated that the diffuser section 110, muffling section 120, and/or removable end cap 130 may be discrete sections with discrete components, may be combined in whole or in part, and/or may have substantially the same or differing lengths, depending on the particular implementation at hand.

The diffuser section 110, which can also be generally referred to as a first chamber of the muffler assembly, is adapted to expand exhaust gas entering the muffler assembly via exhaust inlet 140. Preferably, the diffuser section 110 extends from a first end 150 of the muffler assembly toward a second end 160 of the muffler assembly, and is the front-most section of the muffler assembly (not including exhaust inlet 140). According to one aspect of the present invention, the angled portion of the diffuser section 110 is about 3.00″ or more in length (i.e., the length from the first end 150 toward the second end 160 parallel to a central axis of the muffler assembly).

As shown best in FIG. 6, the diffuser section 110 is preferably of a double walled configuration, and may include an inner wall 112 and an outer wall 114. The inner wall 112 may be made from a substantially solid material, such as a carbon steel, stainless steel or aluminum sheet metal, so as to have a substantially smooth inner surface. The outer wall 114 may be made of a like or different material.

The center line of the exhaust inlet 140 may be offset from a centerline of the diffuser section 110 as shown. In this regard, the center line offset may be in the range of about 1″ to about 1.5″, preferably about 1.25″. Due to this center line offset, the inner wall 112 has a departure angle away from the exhaust inlet 140 at a first angle θ₁, on a first side, and at a second angle θ₂ on a second side. Preferably, first angle θ₁, is in the range of about 40° to about 50°, more preferably about 42.67°. Preferably, second angle θ₂ is in the range of about 10° to about 15°, more preferably about 11.20°. Additionally, it should be appreciated that, while only angles in reference to inner wall 112 have been discussed, the inner wall 112 may be substantially parallel to the outer wall 114. Furthermore, one or both of inner wall 112 and/or outer wall 114 may be angled up to about 5.00″ into the muffler assembly, though preferably up to about 3.00″ as previously discussed.

As shown best in FIG. 1, the muffling section 120 preferably extends from the diffuser 110 toward the second end 160 of the muffler assembly, and can also be generally referred to as a second chamber of the muffler assembly. The muffling section 120 may include an inner wall 122 and an outer wall 124, similar in configuration to diffuser section 110. The inner wall 122 may be made from a perforated material, such as a perforated carbon steel, stainless steel or aluminum sheet metal, so as to allow gases to pass therethrough. The outer wall 124 may be made of a like or different material.

In manufacturing diffuser section 110 and/or muffling section 120, a sheet metal material may be used. In this regard, the sheet metal material may be rolled to achieve a substantially obround shape, as shown, for example, in FIGS. 2-4. Once rolled into the desired shape, edges of the sheet metal material may be fastened together (e.g., welded or riveted) so as to form a seam along a length of the muffler assembly. This seam can then be grounded smooth, polished, chromed, machined, and/or oriented so as to minimize any reduction in the aesthetic qualities of the muffler assembly. Other manufacturing techniques are also contemplated.

As shown best in FIG. 6, removable end cap 130 is preferably positioned at the second end 160 of the muffler assembly. The removable end cap 130 may include a plate 132 fastened thereto, and an insert 134 coupled to the plate 132 (e.g., via welding). The plate 132 may include at least one opening through which exhaust gases exit the muffler assembly. Alternatively, the plate 132 may include a plurality of openings selected to achieve a particular gas flow rate or sound emission. Similarly, insert 134 preferably includes a periphery, width, and/or length selected to achieve a particular gas flow rate or sound emission. In this regard, different plate 132 and/or inserts 134 may be used to achieve different results. Plate 132 and/or insert 134 may be removably attached as the removable part of a fixed end cap 130, or fixed to a replaceable and removable end cap 130. Both embodiments can be generally referred to as a removable end cap 130. In either case, the removable portion may be attached to the muffler assembly using any number of fasteners, such as screws, bolts, magnets, etc. Sealing between the removable end cap 130 and the rest of the muffler assembly may be achieved using a suitable sealing member, such as an “O” ring 136, positioned to inhibit leakage of exhaust gasses between the removable end cap 130 and the muffler assembly or, in an alternative embodiment, between the plate 132 fixed to the removable end cap 130 and the muffler assembly. Use of a suitable sealing member permits the removable end cap 130 to be removed, replaced and reliably resealed as might be performed to install a new removable end cap 130 such as to change the flow rate or sound emission on a finished muffler assembly. A method of assembling a muffler assembly may thus include positioning a suitable sealing member 136 before or during emplacement of the removable end cap 130.

It should be appreciated that one or more components of the removable end cap 130 (e.g., the insert 134) may extend into a third chamber of the muffler assembly, or the third chamber may be eliminated altogether. Preferably, however, no component of the removable end cap 130 substantially extends into the muffling section 120 of the muffler assembly. In this regard, the muffling section 120 is kept baffle free, so as to maximize a flow rate of exhaust through the muffler assembly. Other configurations including one or more baffles in any one or multiple of the three sections are also contemplated, as shown in the exemplary cross sections of FIGS. 2-4, which include optional baffles.

According to one embodiment of the present invention, an insulating material 166 is provided between the inner and outer walls 112, 114 and/or 122, 124 of the diffuser section 110 and muffling section 120 respectively. Preferably, at least ⅛″ thick insulating material 166 is used for such an application. The insulating material 166 is provided to reduce heating of the outer wall 114 and/or 124 due to the temperature of the exhaust gas. By reducing heating of the outer wall 114 and/or 124, heating related discoloration of the outer wall 114 and/or 124 can be reduced or eliminated. Insulating materials such as fiberglass or steel wool may be used, though other materials are also contemplated.

The present inventors have further discovered that, for muffler assemblies having the same outer volume as previously described assemblies, thicker insulating materials 116, such as insulating materials at least ⅜″ thick may be used and provide some advantageous results. Specifically, while a slight reduction in inner volume may be required to accommodate the thicker insulating materials, the present inventors have discovered the thicker insulating material does not substantially reduce performance of the muffler assembly, yet achieves a deeper exhaust tone and quieter overall sound level in comparison to a muffler assembly with ⅛″ thick insulating material. Hence, according to one embodiment of the present invention, an insulating material 166 at least ⅜″ thick is provided. According to another embodiment of the present invention, insulating material 166 has a thickness in the range of about ⅛″ thick to about ⅜″ thick. Other configurations are also contemplated.

The present application may be used to construct a motorcycle muffler assembly with an interior volume (e.g., the region inside of inner wall 112, 114) of about 325 cubic inches, using an outer obround shaped periphery of about 6.25″× about 3.25″. Such a configuration may achieve a sound reduction of more than 3 dB in comparison to known motorcycle muffler assemblies, with improved overall gas flow throughput. Other configurations are also contemplated.

A muffler assembly 800 according to another embodiment of the present invention is shown in FIGS. 8-14. The muffler assembly 800 may be substantially similar to that discussed above with respect to FIGS. 1-7, but includes optional mounting brackets 810. Specifically, one or more mounting brackets 810 may be provided for mounting muffler assembly 800 onto a motorcycle (not shown). Additional bracket configurations are also contemplated. Preferably, the mounting structure is provided such that the muffler assembly 800 can be mounted on a motorcycle without substantially reducing a ground clearance and/or cornering clearance of the motorcycle.

The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

Parts List

-   Departure angle θ₁, θ₂ -   Diffuser section 110 -   Exhaust inlet 140 -   First end of muffler 150 -   Inner wall of diffuser 112 -   Inner wall of muffling section 122 -   Mounting bracket 810 -   Muffler assembly 800 -   Muffling section 120 -   Outer wall of diffuser 114 -   Outer wall of muffling section 124 -   Plate 132 -   Insert 134 -   Insulation 166 -   Removable end cap 130 -   “O” ring sealing member 136 -   Second end of muffler 160 

1. A muffler assembly including a body having a first end and a second end, the muffler assembly comprising: a diffuser extending from the first end of the body toward the second end of the body, the diffuser being adapted to expand exhaust gas entering the muffler assembly; an insert positioned at the second end of the body, the insert including at least one opening through which exhaust gas passes to exit the muffler assembly; and a baffle-less sound dampening portion between the diffuser and the insert, the baffle-less sound dampening portion being adapted to muffle engine sound.
 2. The muffler assembly of claim 1, wherein the body is double walled at least throughout the baffle-less sound dampening portion.
 3. The muffler assembly of claim 2, wherein insulation is provided between an inner wall of the body and an outer wall of the body.
 4. The muffler assembly of claim 3, wherein at least ⅛″ thick insulation is provided between the inner wall of the body and the outer wall of the body.
 5. The muffler assembly of claim 4, wherein the insulation has a thickness in the range of about ⅛″ to about ⅜″.
 6. The muffler assembly of claim 2, wherein an inner wall of body comprises a perforated sheet metal.
 7. The muffler assembly of claim 1, wherein an angle between an exhaust inlet tube and an inner wall of the diffuser is in the range of about 40° to about 50°.
 8. The muffler assembly of claim 7, wherein the angle between the exhaust inlet tube and the inner wall of the diffuser is about 42.67°.
 9. The muffler assembly of claim 1, wherein an angle between an exhaust inlet tube and an inner wall of the diffuser is in the range of about 10° to about 15°.
 10. The muffler assembly of claim 9, wherein the angle between the exhaust inlet tube and the inner wall of the diffuser is about 11.20°.
 11. The muffler assembly of claim 1, wherein the diffuser includes an inner wall of solid sheet metal.
 12. The muffler assembly of claim 11, wherein the diffuser further includes insulation between the inner wall of the diffuser and an outer wall of the diffuser.
 13. The muffler assembly of claim 12, wherein at least ⅛″ thick insulation is provided between the inner wall of the diffuser and the outer wall of the diffuser.
 14. The muffler assembly of claim 1, wherein an interior volume of the muffler assembly is at least 325 cubic inches.
 15. The muffler assembly of claim 1, wherein the insert positioned at the second end of the body comprises a removable end cap.
 16. The muffler assembly of claim 1, wherein the insert positioned at the second end of the body is attached to a plate mounted to the muffler assembly by a plurality of fasteners.
 17. The muffler assembly of claim 1, wherein the insert positioned at the second end of the body includes a plurality of openings through which exhaust gas passes to exit the muffler assembly.
 18. The muffler assembly of claim 1, wherein the body is made of one of carbon steel, stainless steel and aluminum.
 19. A muffler assembly comprising: means for expanding exhaust gas entering the muffler assembly; means for controlling exit of exhaust gas from the muffler assembly; and means for baffle-lessly muffling engine sound.
 20. The muffler assembly of claim 19, further comprising means for insulating an inner wall of the muffler assembly from an outer wall of the muffler assembly.
 21. The muffler assembly of claim 19, further comprising means for removably fastening the means for controlling exit of exhaust gas from the muffler assembly.
 22. The muffler assembly of claim 19, wherein the muffler assembly is made of one of carbon steel, stainless steel and aluminum.
 23. A double walled muffler assembly for a motorcycle, comprising: a diffuser section comprised of: a solid inner wall; an outer wall; and insulation provided between the inner and outer walls of the diffuser section, wherein an angle between an inlet tube and the inner wall of the diffuser is in the range of about 40° to about 50°; a baffle-less muffling section comprised of: a perforated inner wall; an outer wall; and insulation provided between the inner and outer walls of the baffle-less muffling section; and a removable end cap including at least one opening through which exhaust gases exit the double walled muffler assembly.
 24. A double walled exhaust muffler assembly for a motorcycle, comprising: a body having a substantially obround periphery; an inlet for receiving exhaust gas from a motorcycle engine; and an outlet for exhausting exhaust gas from the muffler assembly, wherein the muffler assembly is mountable on the motorcycle such that a ground clearance of the motorcycle is not reduced by the muffler assembly, and wherein an interior volume of the muffler assembly is at least 325 cubic inches. 